1. Field of the Invention
The present teachings relate to lubricity additives for fuels and methods to use the additives in fuels.
2. Discussion of the Related Art
Monocarboxylic acids, or fatty acids, have long been recognized as effective lubricity additives for diesel fuels. Unfortunately, many commercially available fatty acids and fatty acid blends tend to freeze or form crystals at temperatures common during winter weather. The freezing or formation of crystals makes handling of the additives, and particularly injection into fuel difficult. Blending the fatty acid with a solvent can reduce the crystal formation temperature, or cloud point. However, addition of a solvent will increase cost and complexity.
The fatty acids, fatty acid ammonium salts and fatty acid amides presently used have the disadvantage of solidifying on storage at low temperatures, frequently even at room temperature, usually at temperatures of 0° C., or crystalline fractions separate and cause handling problems. Diluting the additives with organic solvents only partly solves the problem, since fractions will still crystallize out from solutions or the solution will gel and solidify. Thus, for use as lubricity additives, the fatty acids, fatty acid ammonium salts and fatty acid amides either have to be greatly diluted or kept in heated storage vessels and added via heated pipework.
The present teachings provide lubricity additives that enhance the lubricity of fuels, especially middle distillate fuels, and remain homogeneous, clear and flowable at low temperatures. Additionally, the cold flow properties of middle distillate fuels are not adversely affected.
A need exists, therefore, for enhancement of lubricity additive formularies, to result in a lowering of the cloud point, without deleterious effects on other desired properties.